Differential apparatus

ABSTRACT

A differential apparatus includes a differential mechanism, a differential case that accommodates the differential mechanism, and a clutch mechanism that transmits a driving force between the differential case and the differential mechanism. The clutch mechanism includes a slide member movable inside the differential case in an axial direction and an actuator. The slide member has a first meshable portion at one end in the axial direction, is allowed move relative to the differential mechanism in the axial direction, and is prevented from rotating relative to the differential mechanism. The differential case includes a first case member and a second case member that are united to form the differential case. The first case member integrally includes a second meshable portion and a flange portion that the ring gear is fastened to. When the actuator is activated the first meshable portion meshes with the second meshable portion so that the differential case and the slide member are coupled to present a relative rotation between the differential case and the slide member.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-077431 filed onApr. 7, 2016 including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a differential apparatus that allows an inputdriving force be deferentially outfitted from a pair of output members.

2. Description of Related Art

Differential apparatuses that allow an input driving force to bedifferentially outputted from a pair of output members have been used,for example, as differentials in vehicles. Some of this type ofdifferential apparatuses can interrupt the transmission of the inputdriving force to the output members, as disclosed in, for example,Japanese Patent Application Publication No. 2015-87015 A).

The differential apparatus disclosed in JP 2015-87015 A includes adifferential mechanism having two differential gears supported on ashaft-shaped journal and two sideshaft gears, a differential case(housing) that accommodates the differential mechanism, a carrierelement rotatably accommodated in the differential case, a second clutchsection fixed to the carrier element, a first clutch section engageablewith the second clutch section, and an actuator for moving the firstclutch section relative to the second clutch section in an axialdirection. A driving force is inputted to the differential case from adriving gear that is welded or bolted to the outer circumferentialsurface of the differential case. The carrier element has two bores, andthe journal is inserted through the bores and fixed by a securing pin.

The first clutch section includes an annular portion and multiple axialprojections projecting from the annular portion in the axial direction.The tip end of each axial projection is provided with a toothed ringsegment engageable with the second clutch section. The annular portionof the first clutch section is located outside the differential case,and the axial projections of the first clutch section are insertedthrough axial holes in a side wall of the differential case. Thiscouples the first clutch section to the differential case in a mannerthat allows the first clutch section to move relative to thedifferential case in the axial direction and that prevents the firstclutch section from rotating relative to the differential case.

When the first clutch section moves toward the second clutch section inthe axial direction by actuation of the actuator, the toothed ringsegments of the axial projections engage with the second clutch section,so that the carrier element rotates along with the differential case.Thus, the driving force inputted to the differential case from thedriving gear is transmitted to the differential gears via the firstclutch section, the second clutch section, and the carrier element.

In contrast, when the actuator deactivated, the first clutch section isseparated from the second clutch section by a return spring. Thisdisengages the first clutch section from the second clutch section,thereby allowing the carrier element to rotate relative to thedifferential case. Accordingly, the transmission of the driving force tothe differential mechanism from the differential case is interrupted.

According to the differential apparatus disclosed in JP 2015-87015 A,the driving force inputted to the differential case is transmitted tothe first clutch section through the side wall of the differential case.Since the side wall has multiple axial holes that the axial projectionsare inserted through, the side wall may be hard to have sufficientstructural strength. Increasing the thickness of the differential casemay allow the side wall to have sufficient strength to transmit enoughdriving force to the first clutch section. However, the increase in thethickness of the differential case increases the weight and size of thedifferential case accordingly.

SUMMARY OF THE INVENTION

An object of the invention is to provide a differential apparatus thatselectively transmits a driving force and that reduces an increase inthe weight and size of a differential case.

An aspect of the invention provider a differential apparatus including adifferential mechanism that allows a driving force inputted to an inputmember to be differentially distributed to a pair of output members, adifferential case that accommodates the differential mechanism, and aclutch mechanism that transmits the driving force between thedifferential case and the input member of the differential mechanism.The clutch mechanism includes a slide member and an actuator. The slidemember is arranged in a manner that allows the slide member to moverelative to the differential mechanism inside the differential case in acentral axial direction along a rotation axis of the differential caseand that does not allow the slide member to rotate relative to thedifferential mechanism inside the differential case. The actuatorsupplies the slide member with a moving force that moves the slidemember in the central axial direction. The slide member includes a firstmeshable portion that is located at one end of the slide member in thecentral axial direction and that has multiple meshable teeth. Thedifferential case includes multiple case members that an united to formthe differential case. A first case member of the case members includesa second meshable portion having multiple meshable teeth facing thefirst meshable portion in the central axial direction. The first casemember further includes a joint portion that an input gear that rotatesalong with the differential case is joined to. The differentialapparatus switches between a coupled state and a decoupled state inaccordance with whether the actuator is activated or deactivated. Thecoupled state causes the first meshable portion and the second meshableportion to mesh with each other in a circumferential direction so thatthe differential case and the slide member are coupled not to allow arelative rotation between the slide member and the differential case.The decoupled state decouples the differential case and the slide memberfrom each other to allow the relative rotation between the slide memberand the differential case.

This aspect of the differential apparatus induces an increase in theweight and size of the differential case and selectively transmits thedriving force.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further features and advantages of the invention willbecome apparent from the following description of example embodimentsreference to the accompanying drawings, wherein like numerals are usedto represent like elements and wherein:

FIG. 1 is a sectional view illustrating an example structure of adifferential apparatus according to a first embodiment of the invention;

FIG. 2 is an exploded perspective view illustrating the differentialapparatus;

FIG. 3 is a perspective view illustrating a slide member of thedifferential apparatus;

FIG. 4 is a perspective view illustrating a differential mechanism ofthe differential apparatus;

FIG. 5 is an exploded perspective view illustrating the differentialmechanism;

FIG. 6 is an enlarged partial sectional view illustrating thedifferential apparatus;

FIG. 7A is an explanatory diagram illustrating how the differentialapparatus operates when an actuator is deactivated;

FIG. 7B is an explanatory diagram illustrating how the differentialapparatus operates when the actuator is activated;

FIG. 8 is an exploded perspective view illustrating a differentialmechanism and a slide member according to a second embodiment of theinvention;

FIG. 9 is a partial cross-sectional view illustrating first, second, andthird pinion shafts of the differential mechanism and illustratingcross-sections of a first supporting member and a second supportingmember; and

FIG. 10 is a diagram illustrating a pinion gear support member as aninput member of a differential mechanism according to a third embodimentof the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

A first embodiment of the invention is described with reference to FIG.1 through FIG. 7B.

FIG. 1 is a sectional view illustrating an example structure of adifferential apparatus 1 according to the first embodiment of theinvention. FIG. 2 an exploded perspective view illustrating thedifferential apparatus 1. FIG. 3 is a perspective view illustrating aslide member 5 of the differential apparatus 1. FIG. 4 is a perspectiveview illustrating a differential mechanism 3 of the differentialapparatus 1. FIG. 5 is an exploded perspective view illustrating thedifferential mechanism 3. FIG. 6 is an enlarged partial sectional viewillustrating the differential apparatus 1. FIG. 7A is an explanatorydiagram illustrating how the differential apparatus 1 operates when anactuator 6 is deactivated. FIG. 7B is an explanatory diagramillustrating how the differential apparatus operates when the actuator 6is activated.

The differential apparatus 1 is used to allow a driving force of avehicle driving source, such as an engine to be differentiallydistributed to a pair of output shafts. Specifically according to thisembodiment, the differential apparatus 1 is mounted on afour-wheel-drive vehicle that has a pair of right and left main drivewheels (e.g., front wheels) and a pair of right and left auxiliary drivewheels (e.g., rear wheels). The driving force of the driving source isalways transmitted to the pair of right and left main drive wheels andis selectively transmitted to the pair of right and left auxiliary drivewheels depending on traveling conditions. The differential apparatus 1is used as a differential for distributing the driving force to the pairof right and left auxiliary drive wheels. When the driving force istransmitted to only the main drive wheels, the vehicle operates in atwo-wheel drive mode. When the driving force is transmitted to both themain drive wheels and the auxiliary drive wheels, the vehicle operatesin a four-wheel drive mode. When the vehicle operates in a four-wheeldrive mode, the differential apparatus 1 distributes an input drivingforce to right and left drive shafts for the auxiliary drive wheels.

The differential apparatus 1 includes a differential case 2 rotatablysupported by a differential carrier that is not illustrated in thedrawings, a differential mechanism 3 accommodated in the differentialcase 2, and a clutch mechanism 4 that selectively transmits the drivingforce between the differential case 2 and the differential mechanism 3.Lubricating oil is introduced in the differential case 2 to lubricatethe differential mechanism 3.

The differential mechanism 3 includes a pinion shaft 30 as an inputmember, multiple (four in this embodiment) pinion gears 31 supported torevolve around a rotation axis O of the differential case 2, and a pairof side gears 32 as a pair of output members. The pinion gears 31 andthe pair of side gears 32 are bevel gears and are in mesh with eachother with their gear axes perpendicular to each other. One of the pairof side gears 32 is coupled to the right drive shaft and is presentedfrom rotating relative to the right drive shaft. The other of the pairof side gears 32 is coupled to the left drive shaft and is preventedfrom rotating relative to the left drive shaft. Although the piniongears 31 and the side gears 32 have actually gear teeth, FIGS. 2, 4, and5 omit the illustration of the gear teeth for the sake of simplicity.

The differential mechanism 3 allows the driving force inputted to thepinion shaft 30 to be differentially outputted to the pair of driveshafts. According to this embodiment, the differential mechanism 3 has apair of pinion shafts 30. Two of the four pinion gears 31 are rotatablysupported on one pinion shaft 30, and the other two of the four piniongears 31 are rotatably supported on the other pinion shaft 30.

As shown in FIG. 5, each pinion shaft 30 integrally includes a pair ofengaged portions 301 that are engaged with a slide member 5 of theclutch mechanism 4 as described later, a pair of pinion gear supportingportions 302 that are inserted through the pinion gears 31, and aconnector 303 that connects the pair of pinion gear supporting portions302 together. As a whole, each pinion shaft 30 has a shaft shape. One ofthe pair of engaged portions 301 is located at one end of the pinionshaft 30. The other of the pair of engaged portions 301 is located atthe other end of the pinion shaft 30. The connector 303 is located at amiddle portion of the pinion shaft 30 in an axial direction of thepinion shaft 30. Each pinion gear supporting portion 302 is locatedbetween the engaged portion 301 and the connector 303 and rotatablysupports the pinion gear 31.

The pair of the pinion shafts 30 engage with each other at their middleportion in their axial direction. Specifically, the connector 303 of onepinion shaft 30 is fitted into a recess formed between the pair ofpinion gear supposing portions 302 of the other pinion 30, and theconnector 303 of the other pinion shaft 30 is fitted into a recess 300formed between the pair of pinion gear supporting portions of one pinionshaft 30. The pair of pinion shafts 30 are perpendicular to each otherwhen viewed from a direction along the rotation axis O of thedifferential case 2.

The clutch mechanism 4 includes the slide member 5 movable in a centralaxial direction along the rotation axis O of the differential case 2,the actuator 6 for supplying the slide member 5 with a moving force thatmoves the slide member 5 in the central axial direction, and a pressingmember 7 located between the slide member 5 and the actuator 6. Theslide member 5 is located inside the differential case 2. The actuator 6is located outside the differential case 2. The pressing member 7transmits the moving force of the actuator 6 to the slide member 5. Theslide member 5 is pressed and moved in the central axial direction bythe pressing member 7.

The slide member 5 has a round cylindrical shape with a central axis incoincidence with the rotation axis O of the differential case 2. Theslide member 5 is arranged in a manner that allows the slide member 5 tomove relative to the differential mechanism 3 in the central axialdirection along the rotation axis O of the differential case 2 and thatprevents the slide member 5 from rotating relative to the differentialmechanism 3. The slide member 5 is formed by forging a steel material.As shown in FIG. 3, the slide member 5 integrally includes a firstmeshable portion 51 that is located at one end of the slide member 5 inthe central axial direction and that has multiple meshable teeth 510, anannular inner rib portion 52 projecting toward the inside of the firstmeshable portion 51, and a cylindrical portion 53 having engagingportions 530 that engage with the pinion shafts 30 in a circumferentialdirection. The first meshable portion 51 is meshable with a secondmeshable portion 211 of the differential case 2 in the circumferentialdirection. The second meshable portion 211 is described later. Eachengaging portion 530 goes through the cylindrical portion 53 between theinner and outer circumferential surfaces of the cylindrical portion 53and is formed as a groove extending in the central axial direction ofthe slide member 5.

Each engaging portion 530 engages with the corresponding engaged portion301 located at each end of the pinion shaft 30. The engagement of theengaged portions 301 of the pinion shafts 30 with the engaging portions530 of the slide member 5 allows the slide member 5 to move in thecentral axial direction relative to the pinion gears 31 that arerotatably supported on the pinion shafts 30 while preventing the slidemember 5 from rotating relative to the pinion gears 31. The pinion gearsresolve around the rotation axis O of the differential case 2 along withthe slide member 5. Specifically, the pinion gears 31 revolve around therotation axis O while the slide member 5 rotates on the rotation axis O.According to tins embodiment, the cylindrical portion 53 has fourengaging portions 530 so that all the engaged portions 301 located atthe ends of the pinion shafts 30 can be engaged with the slide member 5.

As shown in FIG. 7A and FIG. 7B, a washer 33 is located between a backsurface 31 a of each of the pinion gears 31 and an inner circumferentialsurface 53 a of the cylindrical portion 53 of the slide member 5. Aninner surface 33 a of the washer 33 is partly spherical and faces theback surface 31 a of the pinion gear 31. An outer surface 33 b of thewasher 33 is flat and faces the inner circumferential surface 53 a ofthe cylindrical portion 53 of the slide member 5. When the pinion gear31 rotates on the pinion shaft 30, the back surface 31 a of the piniongear 31 slides on the inner surface 33 a of the washer 33. When theslide member 5 moves in the central axial direction relative to thepinion shafts 30, the inner circumferential surface 53 a of thecylindrical portion 53 of the slide member 5 slides on the outer surface33 b of the washer 33.

The cylindrical portion 53 of the slide member 5 has multiple openings531 that lubricating oil flows through. According to this embodiment,the cylindrical portion 53 has four openings 531 that are equally spacedfrom each other in the circumferential direction of the cylindricalportion 53. Each opening 531 goes through the cylindrical portion 53 inthe radial direction of the cylindrical portion 53 and has an open endon the side opposite to the side where the first meshable portion 51 islocated. The number and shape of the openings 531 are not limited tothose described above. The cylindrical portion 53 can have any number ofthe openings 531 of any shape.

The inner rib portion 52 of the slide member 5 has an annular receivingsurface 52 a that receives a biasing forces of a biasing member 81 asdescribed later. The inner rib portion 52 further has multiple fittingportions 520 that are separately fitted with multiple projections 821(refer to FIG. 2) of a retainer 82 that retains the biasing member 81.The fitting portions 520 are recessed in the receiving surface 52 a.

The pressing member 7 has a ring portion 71 and multiple leg portions72. The ring portion 71 abuts against an axial end surface 53 b of thecylindrical portion 53 of the slide member 5. The axial end surface 53 bis located on the side opposite to the side where the first meshableportion 51 is located. The leg portions 72 extend from the ring portion71 in a direction parallel to the rotation axis O of the differentialcase 2. According to this embodiment, the pressing member 7 has threeleg portions 72. The pressing member 7 is formed by press working from asteel sheet, and a tip end of each leg portion 72, opposite to a baseend where the ring portion 71 is located, is bent inward.

The actuator 6 includes an annular electromagnet 61, a yoke 62, and anarmature 63. The annular electromagnet 61 has a coil winding 511 and amolding resin member 612 that encapsulates the coil winding 611. Theyoke 62 provides a magnetic path for magnetic flux that is generated bythe electromagnet 61 when the coil winding 611 is energized. Thearmature 63 is guided in the direction of the rotation axis O of thedifferential case 2 while in sliding contact with the molding resinmember 612. The molding resin member 612 is rectangular in section alongthe rotation axis O. A magnetic force generated by energizing the coilwinding 611 causes the armature 63 to move the slide member 5 in such adirection that the first meshable portion 51 meshes with the secondmeshable portion 211 of the differential case 2. The moving force of theactuator 6 is transmitted to the slide member 5 through the pressingmember 7, thus causing the first meshable portion 51 of the slide member5 to mesh with the second meshable portion 211.

The coil winding 611 is supplied with an exciting current via anelectric wire 610 (refer to FIG. 2) from a controller that is notillustrated in the drawings. Supplying the exciting current to the coilwinding 611 activates the actuator 6. Since the actuator 6 is locatedoutside the differential case 2, it is easy to supply the current to thecoil winding 611. The yoke 62 is made of a soft magnetic metal such aslow-carbon steel. As shown in FIG. 6, the yoke 62 integrally includes acylindrical portion 621 and a rib portion 622. The cylindrical portion621 covers an inner circumferential surface 612 b of the molding resinmember 612 from inside. The rib portion 622 projects outwardly from anaxial end portion of the cylindrical portion 621 and covers an axial endsurface 612 c of the molding resin member 612. The bore diameter of thecylindrical portion 621 is slightly larger than the outside diameter offacing portion of the differential case 2 that faces an innercircumferential surface 621 a of the cylindrical portion 621.

The circumferential surface 621 a of the cylindrical portion 621 has anannular recess 640 that multiple (three in this embodiment) plates 84fit into. The plates 84 are made of a non-magnetic material and arefixed to the differential case 2 by press-fit pins 83. The fitting ofthe plates 84 into the annular recess 640 prevents the yoke 62 to moverelative to the differential case 2 in the axial direction. The axialwidth of the annular recess 640 is larger than the thickness of theplates 84 so as to prevent a rotational resistance between the yoke 62and the plates 84 when the differential case 2 rotates.

A stopper ring 64 is fixed to an end of the cylindrical portion 621 ofthe yoke 62 that is opposite to the end where the rib portion 622projects. The stopper ring 64 is made of a non-magnetic metal such asaustenite stainless steel and integrally includes an annular portion641, a pair of projections and folded-back portions 643. The annularportion 641 is fixed to the yoke 62. The pair of projections 642 projectfrom the annular portion 641 at two positions on the circumference ofthe annular portion 641. Each of the folded-back portions 643 is foldedback at an acute angle from the tip end of a corresponding one of thepair of projections 642. The pair of projections 642 engage with thedifferential carrier that is not illustrated in the drawings, therebypreventing rotation of the stopper ring 64. The annular portion 641 isfixed to the yoke 62, for example, by welding.

The armature 63 is made of a soft magnetic metal such as low-carbonsteel and integrally includes an outer annular portion 631 locatedaround the electromagnet 61 and a side plate portion 632 that faces theelectromagnet 61 in the axial direction. The outer annular portion 631has a round cylindrical shape and covers the outer circumference of theelectromagnet 61. The side plate portion 632 projects inward from anaxial end of the outer annular portion 631. The side plate portion 632faces an axial end surface 612 d of the molding resin member 612 in theaxial direction. The axial end surface 612 d is opposite to the axialend surface 612 c that faces the rib portion 622 of the yoke 62. Inaddition, the side plate portion 632 faces both the annular portion 641of the stopper ring 64 and an axial end surface 621 b of the cylindricalportion 621 of the yoke 62 in the axial direction.

An inner circumferential surface 631 a of the outer annular portion 631of the armature 63 is in contact with an outer circumferential surface612 a of the molding resin member 612 so that the armature 63 issupported by the electromagnet 61. When the armature 63 moves in theaxial direction, the inner circumferential surface 631 a of the outerannular portion 631 slides on the outer circumferential surface 612 a ofthe molding resin member 612.

As shown in FIG. 2, the side plate portion 632 of the armature 63 hasengagement holes 632 a that engage with the projections 642 of thestopper ring 64, a wire insertion hole 632 b that the electric wire 610is inserted through, and multiple (nine in the example shown in FIG. 2)oil holes 632 c that lubricating oil flows through. The leg portions 72of the pressing member 7 abut against an end portion of the side plateportion 632 on the inner circumferential side of the side plate portion632. The folded-back portions 643 of the stopper ring 64 prevent thearmature 63 from being detached from the stopper ring 64. The engagementof the projections 642 with the engagement holes 632 a prevents thearmature 63 from rotating relative to the differential carrier.Specifically, the protections 642 of the stopper ring 64 are insertedthrough the engagement holes 632 a and engage with the differentialcarrier.

The differential case 2 includes a first case member 21 and a secondcase member 22 that are aligned in the direction of the rotation axis O.The first case member 21 and the second case member 22 are united toform the differential case 2. A flat annular washer 34 is locatedbetween the first case member 21 and the pair of side gears 32 of thedifferential mechanism 3 and is also located between the second casemember 22 and the pair of side gears 32.

The second case member 22 has a round cylindrical shape with a bottomand accommodates the differential mechanism 3 and the slide member 5.The second case member 22 integrally includes a cylindrical portion 221having a round cylindrical shape, a wall portion 222 projecting inwardlyfrom one end of the cylindrical portion 221 that is opposite to the sidewhere the first case member 21 located, and a flange portion 223projecting outwardly from the other end of the cylindrical portion 221.The electromagnet 61 and the yoke 62 are located in a corner formedbetween the cylindrical portion 221 and the wall portion 222.

The cylindrical portion 221 has multiple oil holes 221 a thatlubricating oil flows through. The wall portion 222 has multiple (threein this embodiment) insertion holes 222 a for transmitting the movingforce of the actuator 6 to the slide member 5. The wall portion 222further has a shaft insertion hole 222 b that receives a drive shaftthat is coupled to one of the pair of the side gears 32 so as not torotate relative to the one of the pair of the side gears 32. Each of theleg portions 72 of the pressing member 7 is inserted through acorresponding one of the insertion holes 222 a. The insertion holes 222a and the shaft insertion hole 222 b go through the wall portion 222 inthe direction parallel to the rotation axis O.

The first case member 21 is shaped, for example, by forging and has adisc shape that covers an opening of the second case member 22. Thefirst case member 21 integrally includes the second meshable portion 211with multiple meshable teeth 210 and a flange portion 212 that buttsagainst the flange portion 223 of the second case member 22. The secondmeshable portion 211 faces the first meshable portion 51 in the centralaxial direction of the slide member 5. The slide member 5 is locatedbetween the second meshable portion 211 of the first case member 21 andthe wall portion 222 of the second case member 22. The first case member21 has a shaft insertion hole 21 a that receives a drive shaft that iscoupled to the other of the pair of the side gears 32 so as not torotate relative to the other of the pair of the side gears 32.

A driving force from a ring gear 23 (refer to FIG. 1) as an input gearis inputted to the differential case 2. The ring gear 23 is fixed to theflange portions 212 and 223 of the first and second case members 21 and22. The flange portions 212 and 223 serve as a joint portion that thering gear 23 is joined to. According to this embodiment, the flangeportion 212 of the first case member 21 has multiple bolt insertionholes 212 a, and the flange portion 223 of the second case member 22 hasmultiple bolt insertion holes 223 a. The ring gear 23 is fixed to thedifferential case 2 by multiple fastening bolts 24 that are separatelyinserted through the bolt insertion holes 212 a and 223 a. This fixationallows the ring gear 23 to rotate along with the differential case 2.Each of the fastening bolts 24 has a head 241 and a shank 242 with anexternal thread. The head 241 abuts against the flange portion 212 ofthe first case member 21, and the shank 242 is inserted through the boltinsertion holes 212 a and 223 a, so that the fastening bolt 24 isscrewed into a threaded hole 23 a in the ring gear 23.

The ring gear 23 can be fixed to the differential case 2 by methodsother than by bolting. For example, the ring gear 23 may be fixed to thefirst case member 21 by welding. In this case, a portion of the firstcase member 21 that is welded to the ring gear 23 serves as the jointportion.

The first case member 21 and the second case member 22 are united bymultiple coupling bolts 25 (refer to FIG. 2. According to thisembodiment, the first case member 21 and the second case member 22 areunited by four coupling bolts 25 before the ring gear 23 is fastened.FIG. 2 illustrates three of the four coupling bolts 25. The couplingbolts 25 are inserted through bolt insertion holes 223 b in the flangeportion 223 of the second case member 22 and are screwed into threadedholes 212 b in the first case member 21.

The biasing member 81 and the retainer 82 that retains the biasingmember 81 are located between the first case member 21 and the inner ribportion 52 of the slide member 5. The biasing member 81 is an elasticbody. The retainer 82 includes an annular body 820 and three projections821 that extend from the body 820 toward the wall portion 222 of thesecond case member 22. The projections 821 are fitted with the fittingportions 520 of the inner rib portion 52 of the slide member 5 so as toprevent the retainer 82 front rotating relative to the slide member 5.

The biasing member 81 is compressed in the central axial direction ofthe slide member 5 by actuation of the actuator 6. The slide member 5 isbiased toward the wall portion 222 of the second case member 22 by arestoring force (i.e., a biasing force) of the biasing member 81. Forexample, a coil spring can be used as the biasing member 81.Alternatively, the biasing member 81 may be made of rubber. According tothis embodiment, the biasing member 81 is annular in shape and islocated between the differential mechanism 3 and the cylindrical portion221 of the second case member 22. Alternatively, the biasing member 81may be divided in multiple separate portions that are located atdifferent positions and that face the inner rib portion 52 of the slidemember 5.

The differential apparatus 1 switches between a coupled state and adecoupled state in accordance with whether the actuator 6 is activatedor deactivated. In the coupled state, the first meshable portion 51 andthe second meshable portion 211 mesh with each other in thecircumferential direction so that the slide member 5 and thedifferential case 2 are coupled to prevent a relative rotation betweenthe slide member 5 and the differential case 2. In the decoupled state,the slide member 5 and the differential case 2 are decoupled to allowthe relative rotation between the slide member 5 and the differentialcase 2.

FIG. 7A is a partial sectional view illustrating the differentialapparatus 1 seen when the actuator 6 is deactivated. FIG. 7B is apartial sectional view illustrating the differential apparatus 1 seenwhen the actuator 6 is activated.

The actuator 6 is deactivated when no exciting current is supplied tothe coil winding 611 of the electromagnet 61. When the actuator 6 isdeactivated, the restoring force of the biasing member 81 moves theslide member 5 toward the wall portion 222 of the second case member 22,thus disengaging the first meshable portion 51 and the second meshableportion 211 from each other. Further, when the electromagnet 61 isde-energized, the restoring force of the biasing member 81 istransmitted to the armature 63 through the slide member 5 and thepressing member 7, thus returning the armature 63 to an initial positionaway from the wall portion 222.

When the actuator 6 is deactivated, the transmission of the drivingforce from the differential case 2 to the differential mechanism 3 isinterrupted because the differential case 2 and the slide member 5 areallowed to rotate relative to each other. Thus, the driving forceinputted to the differential case 2 from the ring gear 23 is nottransmitted to the drive shafts so that the vehicle operates in atwo-wheel drive mode.

When the exciting current is supplied so the coil winding 611 of theelectromagnet 61, the magnetic force of the electromagnet 61 moves thearmature 63 in the axial direction such that the side plate portion 632of the armature 63 approaches an axial end surface 621 b (refer to FIG.6) of the cylindrical portion 621 of the yoke 62. The pressing member 7presses the slide member 5 toward the first case member 21 accordinglyso that the first meshable portion 51 and the second meshable portion211 mesh with each other. Specifically, the moving force of the armature63 is applied to the tip ends of the leg portions 72 of the pressingmember 7, thus causing the pressing member 7 to press the slide member 5toward the first case member 21. At this time, the ring portion 71 ofthe pressing member 7 abuts against the axial end surface 53 b of thecylindrical portion 53 of the slide member 5 on the side opposite to theside where the first meshable portion 51 is located.

When the first meshable portion 51 and the second meshable portion 211mesh with each other, the driving force inputted from the ring gear 23to the differential case 2 is transmitted to the drive shafts via theslide member 5, the pair of pinion shafts 30, the four pinion gears 31,and the pair of side gears 32. Thus, the vehicle operates in afour-wheel drive mode.

A position sensor 10 detects a position of the armature 63 in the axialdirection and outputs a detect to signal, indicative of the detectedposition, to the controller. The position sensor 10 includes a contactmember 11 and a supporting member 12 that supports the contact member11. The contact member 11 is reciprocable relative to the supportingmember 12 in the direction parallel to the rotation axis O of thedifferential case 2. A tip end of the contact member 11 is in elasticcontact with the side plate portion 632 of the armature 63. Thesupporting member 12 is fixed to the differential carrier. Thecontroller identifies the position of the armature 63 from the detectionsignal of the position sensor 10 and determines, based on the identifiedposition, whether the first meshable portion 51 and the second meshableportion 211 mesh with each other.

The controller activates the actuator 6 that remains inactivated bysupplying the electromagnet 61 with the exciting current having a valuelarge enough to move the slide member 5 quickly. Then, when determiningthat the first meshable portion 51 and the second meshable portion 211mesh with each other, the controller reduces the exciting current to avalue that is relatively small, but enough to keep the first meshableportion 51 and the second meshable portion 211 meshing with each other.This approach reduces power consumption.

As described above, according to the first embodiment, the differentialcase 2 includes the first case member 21 and the second case member 22that are united to form the differential case 2, and the first casemember 21 integrally includes the flange portion 212 that the ring gear23 is fastened to and the second meshable portion 211 to mesh with thefirst meshable portion 51 of the slide member 5. The driving forceinputted from the ring gear 23 is transmitted to the slide member 5through only the first case member 21 out of the first and second casemembers 21 and 22. The driving force is then transmitted from the slidemember 5 to the pinion shaft 30 of the differential mechanism 3. Thus, apath for transmitting the driving force does not include the wallportion 222 of the second case member 22 that has the insertion holes222 a that the leg portions 72 of the pressing member 7 are insertedthrough. This reduces an increase in the weight and of the differentialcase 2 and also allows the driving force to be selectively transmittedin accordance with the axial movement of the slide member 5.

Next, a differential apparatus according to a second embodiment of theinvention is described with reference to FIG. 8 and FIG. 9. Thedifferential apparatus according to the second embodiment differs fromthe differential apparatus 1 according to the first embodiment in thestructure of an input member of a differential mechanism. Hence thestructure of the input member is described. Features similar to thosedescribed in the first embodiment are not described in this embodimentand are denoted in FIG. 8 and FIG. 9 by the same reference numerals asin the first embodiment.

FIG. 8 is an exploded perspective view illustrating a differentialmechanism 3A and a slide member 5 according to this embodiment. FIG. 9is a partial cross-sectional view illustrating first, second, and thirdpinion shafts 35, 36, and 37 of the differential mechanism 3A andillustrating cross-sections of a first supporting member 381 and asecond supporting member 382.

According to this embodiment, the differential mechanism 3A has thefirst, second, and third pinion shafts 35, 36, and 37 that each has ashaft shape. The four pinion gears 31 are rotatably supported by thefirst, second, and third pinion shafts 35, 36, and 37. It is noted thatfor the sake of simplicity, FIG. 8 omits the illustration of the pair ofside gears 32 that mesh with the four pinion gears 31. Each of thefirst, second, and third pinion shafts 35, 36, and 37 serves as an inputmember of the differential mechanism 3A. The differential mechanism 3Afurther has the first supporting member 381 and the second supportingmember 382 that support the first, second, and third pinion shafts 35,36, and 37.

The first pinion shaft 35 integrally includes a pair of engaged portions351 that are engaged with the engaging portions 530 of the slide member5, a pair of pinion gear supporting portions 352 that are insertedthrough the pinion gears 31, and a connector 353 that connects the pairof pinion gear supporting portions 352 together. The second pinion shaft36 has an engaged portion 361 at one end and has a butting portion 363at the other end. The engaged portion 361 is engaged with the engagingportion 530 of the slide member 5. The butting portion 363 butts againstthe connector 353 of the first pinion shaft 35. The second pinion shaft36 further has a pinion gear supporting portion 362 between the engagedportion 361 and the butting portion 363. The pinion gear supportingportion 363 is inserted through the pinion gear 31.

Like the second pinion shaft 36, the third pinion shaft 37 has anengaged portion 371 at one end, a butting portion 373 at the other end,and a pinion gear supporting portion 373 between the engaged portion 371and the butting portion 373. The engaged portion 371 is engaged with theengaging portion 530 of the slide member 5. The butting portion 373butts against the connector 353 of the first pinion shaft 35. The piniongear supporting portion 372 is inserted through the pinion gear 31.

The first, second, and third pinion shafts 35, 36, and 37 are insertedthrough insertion holes 381 a of the first supporting member 381 andinsertion holes 382 a of the second supporting member 382. The firstsupporting member 381 has a round cylindrical shape and is locatedinside the slide member 5. The second supporting member 382 has arectangular cylindrical shape and is located inside the first supportingmember 381. The four pinion gears 31 are located between the firstsupporting member 381 and the second supporting member 382.

Four pins 383 are used to present the first, second, and third pinionshafts 35, 36, and 37 from rotating relative to the first supportingmember 381. FIG. 8 illustrates three of the four pins 383. The firstsupporting members 381 has four pin insertion holes 381 b that the puts383 are separately inserted through. The first supporting member 381further has four oil holes 381 c that lubricating oil flows through. Thefirst pinion shaft 35 has two pin insertion holes 35 a that each islocated between the engaged portion 351 and the pinion gear supportingportion 352. The second pinion shaft 36 has a pin insertion hole 36 abetween the engaged portion 361 and the pinion gear supporting portion362. The third pinion shaft 37 has a pin insertion hole 37 a between theengaged portion 371 and the pinion gear supporting portion 372. The fourpins 383 are fixed in the pin insertion holes 381 b, 35 a, 36 a, and 37a, for example, by press-fit fixation.

The second embodiment achieves the same effect as that described in thefirst embodiment.

Next, a differential apparatus according to a third embodiment of theinvention is described with reference to FIG. 10. The differentialapparatus according to the third embodiment differs from thedifferential apparatus 1 according to the first embodiment in thestructure of an input member of a differential mechanism. Hence thestructure of the input member is described. Features similar to thosedescribed in the first embodiment are not described in this embodimentand are denoted in FIG. 10 by the same reference numerals as in thefirst embodiment.

FIG. 10 is a diagram illustrating a pinion gear supporting member 39 asan input member of the differential mechanism according to thisembodiment. According to this embodiment, the pinion gear supportingmember 39 supports the pinion gears 31, and includes four shaft portions391 and a connector 392 that connects the shaft portions 391 together.Each of the shaft portions 391 includes an engaged portion 391 a and apinion gear supporting portion 391 b. The engaged portion 391 a isengaged with the engaging portion 530 of the slide member 5. The piniongear supporting portion 391 b rotatably supports the pinion gear 31. Thefour shaft portions 391 are radially arranged and formed as a singlepiece such that the pinion gear supporting member 39 has a cross shapewhen viewed from the central axial direction. Each of the four shaftportions 391 is engaged at one end with a corresponding one of theengaging portions 530 of the slide member 5 and also rotatably supportsa corresponding one of the pinion gears 31.

The third embodiment achieves the same effect as that described in thefirst embodiment.

What is claimed is:
 1. A differential apparatus comprising: a differential mechanism that allows a driving force inputted to an input member to be differentially distributed to a pair of output members; a differential case that accommodates the differential mechanism; and a clutch mechanism that transmits the driving force between the differential case and the input member of the differential mechanism, wherein the clutch mechanism includes a slide member arranged in a manner that allows the slide member to move relative to the differential mechanism inside the differential case in a central axial direction along a rotation axis of the differential case and that does not allow the slide member to rotate relative to the differential mechanism inside the differential case, the clutch mechanism further including an actuator for supplying the slide member with a moving force that moves the slide member in the central axial direction, the slide member includes a first meshable portion that is located at one end of the slide member in the central axial direction and that has a first plurality of meshable teeth, the differential case includes a plurality of case members that are united to form the differential case, the plurality of case members including a first case member, the first case member including a second meshable portion having a second plurality of meshable teeth facing the first meshable portion in the central axial direction, the first case member further including a joint portion that an input gear that rotates along with the differential case is joined to, and the differential apparatus switches between a coupled state and a decoupled state in accordance with whether the actuator is activated or deactivated, the coupled state causing the first meshable portion and the second meshable portion to mesh with each other in a circumferential direction so that the differential case and the slide member are coupled not to allow a relative rotation between the slide member and the differential case, the decoupled state decoupling the differential case and the slide member from each other to allow the relative rotation between the slide member and the differential case.
 2. The differential apparatus according to claim 1, wherein the slide member of the clutch mechanism is located inside the differential case, the actuator of the clutch mechanism is located outside the differential case, the moving force of the actuator is transmitted to the slide member through a pressing member that is located between the actuator and the slide member, the plurality of case members further includes a second case member including a wall portion having a plurality of insertion holes, the slide member is located between the second meshable portion and the wall portion, and the pressing member has a plurality of leg portions, each leg portion inserted through a corresponding one of the plurality of insertion holes.
 3. The differential apparatus according to claim 2, wherein the input gear is fixed to the differential case by a plurality of bolts, each of the first case member and the second case member includes a flange portion having a plurality of bolt insertion holes, and each of the plurality of bolts is inserted through a corresponding one of the plurality of bolt insertion holes.
 4. The differential apparatus according to claim 2, wherein the second case member has a round cylindrical shape with a bottom and accommodates the differential mechanism and the slide member, and an opening of the second case member is covered with the first case member. 